Using gas and diesel generators, Green Frog Power provides 310MW of short-term reserve electricity to clients including the National Grid, Western Power and Northern Powergrid. Its co-founders Mark Jones, 54, and Jeremy Taylor, 53, started the Coleshill-based company in 2009 and the following year InfraRed Capital Partners invested £20m for a 52% stake. Profits reached £12.5m last year and the company is spending £150m to build 20 new gas-fired power plants across the UK. Its operating margin of 75% was the highest on the league table.

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